Python 3 - 不理解单行双循环

Question

我在看下面的函数：

# Initialize a network
def initialize_network(n_inputs, n_hidden, n_outputs):
    network = list()
    hidden_layer = [{'weights':[random() for i in range(n_inputs + 1)]} for i in range(n_hidden)]
    network.append(hidden_layer)
    output_layer = [{'weights':[random() for i in range(n_hidden + 1)]} for i in range(n_outputs)]
    network.append(output_layer)
    return network

但是，我特别卡在[{'weights':[random() for i in range(n_inputs + 1)]} for i in range(n_hidden)] 行。我正在尝试将该单行重新创建为一个函数：

def make_weights(n_inputs, n_hidden):
    # for i in range(n_inputs + 1):
        # make a random number?
    # for i in range(n_hidden):
        # make a random number?
    # return array of random numbers?

但是，我不太明白那条线在做什么。它循环输入的数量+ 1次，并创建一个随机数？然后对隐藏输入的数量做同样的事情吗？

我正在寻求对那条线的解释，并帮助将那条线映射成更清晰的函数。

目前使用的资源：

• for loop in Python

Answer 1

一般来说，以下两种是等价的：

result = [obj for sub in iterable for obj in sub]

# and

result = []
for sub in interable:
    for obj in sub:
        result.append(obj)

因此，您的make_weights 函数可以定义如下：

def make_weights(n_inputs, n_hidden):
    result = []
    for i in range(n_hidden):
        weights = {'weights': []}
        for j in range(n_inputs + 1):
            weights['weights'].append(random())

        result.append(weights)

Answer 2

一个等价的for循环可能如下，

results = []
for i in range(n_hidden):
        weights = {'weights': []}
        for j in range(n_inputs + 1):
            weights['weights'].append(random())
        result.append(weights)